Conventional latches are used to restrain the movement of one member or element with respect to another. For example, conventional door latches restrain the movement of a door with respect to a surrounding door frame. The function of such latches is to hold the door secure within the frame until the latch is released and the door is free to open. Existing latches typically have mechanical connections linking the latch to actuation elements such as handles which can be actuated by a user to release the latch. Movement of the actuation elements is transferred through the mechanical connections and will cause the latch to release. The mechanical connections can be one or more rods, cables, or other suitable elements or devices. Although the following discussion is with reference to door latches (e.g., especially for vehicle doors), the background information provided applies equally to a wide variety of latches used in other applications.
Most current vehicle door latches contain a restraint mechanism for preventing the release of the latch without proper authorization. When in a locked state, the restraint mechanism blocks or impedes the mechanical connection between the handle and a latch release mechanism, thereby locking the door. Many conventional door latches also have two or more lock states, such as unlocked, locked, child locked, and dead locked states. Inputs to the latch for controlling the lock states of the latch can be mechanical, electrical, or parallel mechanical and electrical inputs. For example, by the turn of a user's key, a cylinder lock can mechanically move the restraint mechanism, thereby unlocking the latch. As another example, cable or rod elements connecting a door handle to the latch release mechanism can be controlled by one or more electrical power actuators. These actuators, sometimes called “power locks” can use electrical motors or solenoids as the force generator to change between locked and unlocked states.
A number of problems exist, however, in the conventional door latches described above. For example, conventional restraint mechanisms in such latches are typically quite complex, with numerous parts often having relatively complicated movements. Such latches are thus more expensive to manufacture, maintain, and repair. This problem is compounded in latches having multiple lock states as mentioned above. These latches often require separate sets of elements corresponding to and controlling each lock state of the latch. Related to this problem are the problems of latch weight and size. The inclusion of more elements and more complex mechanisms within the latch generally undesirably increases the size and weight of the latch. In virtually all vehicle applications, weight and size of any component is a concern. Additionally, increased weight and size of elements and assemblies within the latch necessarily requires more power and greater force to operate the latch. Because power is also at a premium in many applications (especially in vehicular applications), numerous elements and complex assemblies within conventional door latches are an inefficiency that is often wrongly ignored. Not only are larger and more complex latches a power drain, but such latches are typically unnecessarily slow.
Another problem with conventional door latches relates to their operation. Particularly where a latch has multiple lock states, the ability of a user to easily and fully control the latch in its various lock states is quite limited. For example, many latches having a child locked state (i.e., the inside door handle is disabled but the outside door handle is not) require a user to manually set the child locked state by manipulating a lever or other device on the latch. Other latches do not permit the door to enter a dead locked state (i.e., both the inside and outside door handles being disabled). Also, conventional door latches generally do not permit a user to place the door latch in all lock states remotely, such as by a button or buttons on a key fob. These examples are only some of the shortcomings in existing door latch operability.
Still another problem of conventional door latches is related to power locks. The design of existing power lock systems has until now significantly limited the safety of the latch. Latch design limitations exist in conventional latches to ensure, for example, that dead locked latches operated by powered devices or systems will reliably unlock in the event of power interruption or failure. Such limitations have resulted in latch designs which permit less than optimal user operability. Therefore, a reliable design having a failure mode for an electrically powered latch which is electrically actuatable in all locked states remains an elusive goal.
In conventional door latches, yet another problem is caused by the fact that an unauthorized user can often manipulate the restraint mechanism within the latch and/or the connections of the latch to the door locks to unlock the latch. Because existing conventional door latches have at least some type of mechanical linkage from the user-actuated elements (e.g., lock cylinders) to the restraint mechanism in the latch, the ability of an unauthorized user to unlock the latch as just described has been a persistent problem.
In light of the problems and limitations of the prior art described above, a need exists for a latch assembly which has the fewest elements and assemblies possible, is smaller, faster, and lighter than existing latches, consumes less power in operation, is less expensive to manufacture, maintain, and repair, provides a high degree of flexibility in user operation to control the lock states of the latch, has a reliable design in the event of power interruption or failure, and offers improved security against unlocking by an unauthorized user. Each preferred embodiment of the present invention achieves one or more of these results.